Gear burnisher method and apparatus

ABSTRACT

In a gear burnishing system having burnishing gear positions arranged around a subject gear at its center, a burnishing gear is formed as a scraper gear retained on a shaft rotationally by a keyway formed in an inner bore of the scraper gear which is wider by a predefined gap than a corresponding key formed on the shaft such that the scraper gear can move angularly by a small amount for maximum contact on the subject gear. In a preferred embodiment, a number of scraper gears are arranged in a stack on the shaft. Both ends of each scraper gear are beveled along the peripheral edges to cause each tooth to be raked and to create knife blades and serve to trap debris. Each tooth is formed with equal blade angles and a recess with compound angles for debris entrapment. The scraper gears can be mounted with bearings for limited gimbal movement to assure following the subject gear.

This U.S. patent application claims the priority filing date of U.S. Provisional Application 60/884,699 filed on Jan. 12, 2007, of the same title and by the same inventor in the present application.

FIELD OF INVENTION

The present invention relates to a method and apparatus to remove nicks, burrs, scales from heat-treat process, and other surface defects from mechanical gears.

BACKGROUND OF INVENTION

The conventional gear burnishing process involves the use of three burnishing gears and a subject (“to be finished”) gear arranged in a star pattern, with the subject gear in the geometric center. The burnishing gears located at 4 and 8 o'clock have fixed centers, and the burnishing gear at 12 o'clock is vertically moveable to allow for the installation and removal of the subject gear. During the burnishing process, the subject gear is rotationally driven, while at same time, moved axially in a reciprocating fashion. The reciprocating axial motion of the subject gear is intended to maximize its profiled tooth contact with the adjacent burnishing gears and flatten any surface defects. The shortcoming of this system is that because of machining tolerances, and other production procedures, the subject gear tooth and the burnishing gears' teeth only make contact at high points rather than full-length contact, rendering the system inefficient.

SUMMARY OF INVENTION

In a gear burnishing system having a plurality of burnishing gear positions arranged in a star pattern with a subject gear held in its geometric center, the improvement in which a burnishing gear is formed as a “scraper” gear axially retained in position on a shaft at at least one burnishing gear position, wherein the scraper gear is retained on the shaft rotationally by a keyway formed in an inner bore of the scraper gear which is wider by a predefined “gap” than a corresponding key formed on the shaft such that the scraper gear can move angularly by a small amount for maximum contact on the subject gear. The wider keyway allows the scraper gears to increase contact with the subject gear manifold, whereas in the current system there is point contact only.

In a preferred embodiment, a number of scraper gears are arranged in a stack retained on the shaft. With a scraper blade located at the end of each tooth, a subject gear will be subjected to a number of contacts equal to two times the number of gears per stack at each stack location. Both ends of each scraper gear are beveled along the peripheral edges in such a fashion as to cause the end condition of each tooth to be raked and to create knife blades. The bevels also cause peripheral gaps between the scraper gears in the stack which serve the function of trapping debris as they traverse the subject gear during the burnishing process.

The preferred embodiment of the invention is further configured to equalize the blade angles by creating at the end of each tooth a recess with compound angles. One of the angular surfaces equates the angles of the shaving blades, and the other provides the gap needed for debris entrapment.

As further refinements in the preferred embodiment, the scraper gears, individually or as an assembly, can incorporate a spherical type bearing for limited gimbal movement to assure that the burnishing action will follow the lead crown whenever present on the subject gear. The scraper gear is mounted on opposite sides by a pair of bearings to obtain the limited gimbal movement on the shaft.

To facilitate loading and unloading, and to locate a variety of subject gears in the best position, the scraper gear stacks are mounted on adjustable slides which can be adjusted then locked in place to adjust the center distance between them.

Other objects, features, and advantages of the present invention will be explained in the following detailed description of the invention having reference to the appended drawing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A shows a new stack configuration for the burnishing gear of a burnishing gear system having a number of “scraper” gears on a shaft, and FIG. 1B shows an end view thereof.

FIGS. 2A-2D shows a preferred embodiment in which both ends of the burnishing gears are beveled along the peripheral edges.

FIGS. 3A-3D shows the preferred embodiment configured to equalize the blade angles by creating at the end of each tooth a recess with compound angles.

FIG. 4 shows the preferred embodiment of the scraper gear in perspective view.

FIG. 5A and 5B show a further refinement in which the scraper gears are mounted with spherical type bearing for limited gimbal movement, and mounted on slides for center distance adjustment.

DETAILED DESCRIPTION OF INVENTION

The method and apparatus in this invention are configured to remove material during gear burnishing rather than pressing it into the subject tooth profile. The conventional setup is used with three burnishing gear positions arranged in a star pattern, and the subject gear held in the geometric center. However, rather than a single burnishing gear, a number of specially designed narrower “scraper” gears will replace the burnishing gears located at the 4 and 8 o'clock positions. Preferably, each stack of narrower scraper gears at the 4 and 8 o'clock positions will consist of the same number of gears. The pressure gear at the 12 o'clock position remains the same as in the conventional method.

As shown in FIG. 1A, the new stack configuration for the burnishing gear has a number of “scraper” gears 10 (three shown in the drawing) arranged on a shaft 12 which are locked in their axial position by locking collars 14 on their opposite ends on the shaft 12. In the end view shown in FIG. 1B, each scraper gear is retained on the shaft rotationally by a key 12 a formed on the shaft that fits into a keyway 10 a formed in the inner bore of the gear which is wider by a predefined “gap” than the key 12 a. The gap allows the gears to move angularly by a small amount for maximum contact on the subject gear, thereby allowing the stack of scraper gears to increase the number of high point contacts with the subject gear. The wider keyway will allow the stack of scraper gears to increase contact with the subject gear manifold, whereas in the current system there is point contact only. With a scraper blade located at the end of each tooth, a subject gear will be subjected to a number of contacts equal to two times the number of gears per stack at each stack location. For example, if three gears were located at 4 o'clock and three were located at 8 o'clock, the subject gear will be scraped by six blades (three per stack) when moved axially in a reciprocating manner.

In the conventional arrangement, because of the helix angle of the subject gear, the scraper blades will make contact with only one tooth flank (face) at a time. A flank may be defined as the grooved surface of a tooth profile. The end condition of a tooth on a helical gear with flat end faces will have a blade with an acute angle on one flank, and a blade with an obtuse angle on the adjacent flank. The same condition exists at the distal end of the tooth. If such gears were used in the burnishing stack, then cutting or shaving of material on the subject gear will occur on one flank only, leaving defects on the other.

In a preferred embodiment of this invention, as shown in FIGS. 2A-2D, both ends of the burnishing gears are beveled along the peripheral edges in such a fashion as to cause the end condition of each tooth to be raked and to create knife blades. The bevels also cause peripheral gaps between gears in the stack. The gaps serve the function of trapping debris as the scraper gears traverse the subject gear during the burnishing process.

As further shown in FIGS. 3A-3D, the preferred embodiment of the invention is configured to equalize the blade angles by creating at the end of each tooth a recess with compound angles. One of the angular surfaces equates the angles of the shaving blades, and the other provides the gap needed for debris entrapment. The overall preferred scraper gear configuration is shown in perspective view in FIG. 4.

The following further refinements may be made in the preferred embodiment. Referring to FIG. 5A, the second and third burnishing gears located at the 4 and 8 o'clock positions are stacks of scraper gears as previously described, and the first burnishing gear at the 12 o'clock position is a pressure gear as in the conventional configuration. The “scraper” gears disclosed in this invention have a keyway of controlled gap width to establish a loose fit that will allow the scraper gear to adapt to the helix angle of the subject gear. To further improve the work action during the reciprocating motion, the scraper gears, individually or as an assembly, can incorporate a spherical type bearing for limited gimbal movement to assure the burnishing action will follow the lead crown whenever present on the subject gear. In FIG. 5B, the scraper gear is mounted on opposite sides by first and second bearings 50 of the spherical type to obtain the limited gimbal movement on the shaft 52. Each of the keyed gears will rotate on the shaft supported by a bearing on each side. The side bearing supports will increase the strength of the arrangement and provide even support which will improve the quality of the burnishing performance. The loose-fit keyway and the gimbal capability of the mounting can be applied as is best for a specific application.

To facilitate loading and unloading, and to locate a variety of subject gears in the best position, the burnishing gears at position 4 and 8 o'clock are mounted on adjustable slides 54 which can be adjusted then locked in place to adjust the center distance between the scraper gear stacks. Each adjustable slide will have a simplified and cost effective “U” shape mounting for the burnishing gears, which is less complicated and less costly than even a fixed mounting. This capability in conjunction with the actual size (diameter) of the burnishing -gears will locate the subject gear in the best position to receive the pressure and rotation from the burnishing gear on the pressure arm at the 12 o'clock position.

The disclosed improvements provide the specially designed scraper gears with unique cutting or scraping features that will remove unwanted surface flaws from helical and other types of gears in the final stages of production. This invention will allow end users to increase yield and reduce scrap.

It is understood that many modifications and variations may be devised given the above description of the principles of the invention. It is intended that all such modifications and variations be considered as within the spirit and scope of this invention, as defined in the following claims. 

1. In a gear burnishing system having a plurality of burnishing gear positions arranged in a star pattern with a subject gear held in its geometric center, the improvement in which a burnishing gear is formed as a scraper gear axially retained in position on a shaft at at least one burnishing gear position, wherein the scraper gear is retained on the shaft rotationally by a keyway formed in an inner bore of the scraper gear which is wider by a predefined gap than a corresponding key formed on the shaft such that the scraper gear can move angularly by a small amount for maximum contact on the subject gear.
 2. The improvement for a burnishing gear according to claim 1, wherein a number of scraper gears are arranged in a stack retained on the shaft.
 3. The improvement for a burnishing gear according to claim 2, wherein the gear burnishing system has three burnishing gear positions at 4 o'clock, 8 o'clock, and 12 o'clock positions around the subject gear, and a stack of scraper gears is arranged at each of the 4 o'clock and 8 o'clock positions and a pressure gear is arranged at the 12 o'clock position.
 4. The improvement for a burnishing gear according to claim 3, wherein due to the stacks of scraper gears at the 4 o'clock and 8 o'clock positions, a subject gear will be subjected to a number of contacts equal to two times the number of gears per stack at each stack position.
 5. The improvement for a burnishing gear according to claim 4, wherein each stack has 3 scraper gears, and a subject gear will be subjected to six times the number of contacts as compared to a conventional burnishing gear system.
 6. The improvement for a burnishing gear according to claim 2, wherein both ends of each scraper gear are beveled along the peripheral edges in such a fashion as to cause the end condition of each tooth to be raked and to create knife blades, and the bevels cause peripheral gaps between the scraper gears in the stack which serve the function of trapping debris as they traverse the subject gear during the burnishing process.
 7. The improvement for a burnishing gear according to claim 6, wherein on each scraper gear, each tooth thereof has an angular surface formed as a scraper blade and an opposite angular surface formed with compound angled surfaces including an angle that is equal to the angle of the scraper blade and a recess that provides a gap needed for debris entrapment.
 8. The improvement for a burnishing gear according to claim 6, wherein the scraper gear is mounted on the shaft by bearings that provide for limited gimbal movement to assure that the burnishing action will follow a lead crown present on the subject gear.
 9. The improvement for a burnishing gear according to claim 8, wherein the scraper gear is mounted on opposite sides by a pair of spherical type bearings on the shaft.
 10. The improvement for a burnishing gear according to claim 6, wherein the scraper gear stacks are mounted on adjustable slides which can be adjusted then locked in place to adjust the center distance between them.
 11. A method for burnishing a subject gear using a scraper gear according to the improvement in claim
 1. 